Use of mine waste for H₂O₂-assisted heterogeneous Fenton-like degradation of tetracycline by natural pyrite nanoparticles: Catalyst characterization, degradation mechanism, operational parameters and cytotoxicity assessment

Degradation of tetracycline (TTC) with a heterogeneous Fenton-like pyrite/H₂O₂ process by pyrite from mine waste as a mineral catalyst was investigated. The study focused on identifying the main oxidizing agents and degradation mechanisms along with operational variables including solution pH, pyrite and H₂O₂ concentration, contact time, solution temperature, and initial TTC concentration. Catalyst characterization tests revealed that pyrite is a mesoporous powder with a high degree of FeS₂ purity. Radical scavenger tests demonstrated that ^•OH was the main oxidizing agent generated by both solution and surface phase reactions. During the pyrite/H₂O₂ process, more than 85% of TTC was mineralized in 60 min and the maximum TTC removal was attained in the solution at an acidic pH value (4.1). The most abundant transformation products of TTC, formed by the attack of ^•OH radicals, were simple chain carboxylic acids. Cultured cells of human embryonic kidney (HEK) were used for the cytotoxicity assessment of raw and pyrite/H₂O₂ treated TTC solutions. The results illustrated that the viability of HEK cells was enhanced considerably after treating TTC solutions under optimal conditions. Accordingly, pyrite originating from mine waste is a practically effective and cost-effective catalyst in heterogeneous Fenton-like systems for mineralization and degradation of emerging contaminants such as antibiotics.